This invention relates to a combined electrographic printing, copying, and telefax machine. More specifically, the present invention relates to a compact electrographic printing apparatus which is capable of:
(1) scanning and copying an original document, PA1 (2) receiving and printing information derived from a local source, such as information derived from a computer connected to the printing apparatus, PA1 (3) receiving and printing information derived from a remote source, for example, information derived from a remote computer or telefax machine, and PA1 (4) scanning an original document and transmitting the information thereon to a remote source via the telephone lines.
In addition, the printing apparatus is capable of duplex printing, that is, printing on both sides of a sheet of paper.
All of the foregoing printing functions are performed on plain paper using an electrographic or xerographic printing engine which, in one particularly preferred embodiment, includes a disposable cassette containing a photoconductive belt.
In the process of electrographic or xerographic printing, a photoconductive member is employed to record an image on a photosensitive surface. The photoconductive member, which may typically take the form of a belt or a drum, is charged to a substantially uniform potential to sensitize its surface. A light is then employed to discharge selected areas of the photosensitive surface to form an electrostatic latent image on the photoconductive member.
In the case of a copying machine, an original document is exposed to high intensity light. Through the use of a slit aperture, mirrors, and various other optical components, the reflected light image of the original document is shined onto a sensitized photoconductive member where it discharges selected areas of the photosensitive surface. This light image is recorded as an electrostatic latent image on the photoconductive member which latent image corresponds to the informational areas contained on the original document.
In the case of an electrographic printer connected to a computer, a similar process is used to record information on the photoconductive member. The charged portion of the photosensitive surface is exposed to a light image, the shape of which is controlled by input signals from the computer. For example, a laser or an LED array functions as an optical print head and illuminates the photoconductive member with a light image, the characteristic shape of which is controlled by a stream of data from the computer. Here too, an electrostatic latent image corresponding to desired informational areas is recorded on the photoconductive member.
After recording the electrostatic latent image on the photoconductive member, the latent image is developed by bringing a developer material or toner into contact with it. The developer material comprises triboelectrically charged toner particles which are attracted to the electrostatic latent image. The toner particles form a mirror image on the photoconductive member corresponding to the electrostatic latent image. This powder image is subsequently transferred to a sheet of recording medium, such as a sheet of paper, by a transfer unit. In general, the transfer unit comprises a corona charger which creates a high intensity electric field of suitable polarity about the sheet of paper. The powder image, comprising charged toner particles on the photoconductive member are attracted and transferred to the sheet. Thereafter, the powder image is permanently affixed to the sheet in image configuration by a variety of methods such as by fusing, and the sheet is ejected.
The above-mentioned operations may be carried out by arranging a number of stations in sequence about the photoconductive member. Thus, the photoconductive member is usually surrounded in sequence by a charging station to charge the photoconductive member, an imaging station to form an electrostatic latent image on the photoconductive member, a developing station to develop the electrostatic latent image on the photoconductive member, and a transfer station to transfer the developed image from the photoconductive member to the sheet of recording medium. A discharging station and a cleaning station are also arranged about the photoconductive member to ready it for use again.
The assignee of the present invention has disclosed and claimed in a number of patents and patent applications electrographic printer/copiers and components thereof which utilize the above-described principles. A basic objective of the assignee has been to design electrographic printer/copiers from modular components. These modular components can be easily replaced when their useful lives have been exceeded or when they become defective. Another basic objective has been to design electrographic printer/copiers with simplified paper paths which can be easily accessed from the outside in order to remove paper jams. One such electrographic printer/copier employing modular units and a simplified paper path is described in the assignee's U.S. Pat. No. 4,664,507. A photoconductive belt in the form of a disposable cassette with a charging unit attached thereto is described in the assignee's U.S. Pat. No. 4,657,369. Other components are described in U.S. Pat. No. 4,639,116 (developer unit), application Ser. No. 718,945, filed Apr. 2, 1985 (paper input cassette), application Ser. No. 033,458, filed Apr. 1, 1987 (cleaning unit), and application Ser. No. 033,457, filed Apr. 1, 1987 (cleaning unit). All of these components may suitably be used in the electrographic printer/copier of the aforenoted U.S. Pat. No. 4,664,507.
In application Ser. No. 039,464, filed Apr. 16, 1987, the inventors herein have described an electrographic printer/copier similar to the one described in U.S. Pat. No. 4,664,507 but which is also capable of duplex printing, that is, printing on both sides of a sheet of paper. The electrographic printer/copier of that application utilizes the same modular units as the apparatus of U.S. Pat. No. 4,664,507, including the previously mentioned photoconductive belt in the form of a disposable cassette. Other aspects of this duplex printing machine are described and claimed in applications Ser. Nos. 116,362 and 116,363, both filed Nov. 2, 1987.
All of the foregoing patents and patent applications have been assigned to the present assignee and all are incorporated herein by reference.
Telefax transmitting and receiving machines, also known as facsimile machines, resemble electrographic copiers and printers in many respects. Typically, telefax machines include a device for scanning an original document and for digitizing the scanned image, and a printing engine. Advanced high speed, high resolution, telefax machines employ charge-coupled devices (CCD's) for digitizing the scanned image. All CCD's are basically shift registers which digitize analog information and store the digitized information until it is delivered as an electrical signal. CCD's have been utilized as image sending devices for a variety of purposes. In particular, CCD linear arrays have been used as linear sensing devices in high performance telefax machines. To transmit information, such as graphics or text, on a sheet of paper via a telefax machine, the sheet of paper is scanned with a high intensity light and the image is focused onto a CCD linear array. The CCD digitizes the image and converts it into a stream of data, or bit stream. This bit stream, which optionally may be compressed by a variety of known techniques, is then transmitted over the telephone lines to a remote location using a modem.
A telefax machine or a computer at the remote location includes a modem to receive the bit stream over the telephone lines. After decompression when required, the bit stream controls the operation of a print engine to reproduce the information contained on the scanned original document. Telefax machines are known which employ an electrographic process to reproduce the original document at a remote location. Thus, in a process very similar to that described above for a printer, the bit stream received at the remote location can control an optical print head to focus an image on a photoconductive member and thereby produce an electrostatic latent image thereon corresponding to the original document. The electrostatic latent image can then be developed with a toner to form a powder image which is then transferred and fused to a sheet of plain paper.
As copiers, printers and telefax machines can all be adapted to employ an electrographic process to print information on a sheet of recording medium, it would be desirable to provide a single machine which is switchable between copying, printing, and telefax transmitting and receiving modes.
It is therefore an object of the present invention to provide an electrographic printing machine which is capable of:
(1) scanning and copying an original document,
(2) receiving and printing information derived from a local computer,
(3) receiving and printing information derived over the telephone lines from a remote computer or telefax machine, and
(4) scanning an original document and transmitting the information thereon over the telephone lines to a remote computer or telefax machine.
It is a further object of the present invention to provide an electrographic printing machine of the kind just described which is further capable of duplex printing, that is, of printing on both sides of a sheet of paper.
It is a further object of the present invention to provide such a machine which has an input paper cassette and an input paper tray, the input paper tray serving as an alignment correction means for paper being duplex printed.
It is a further object of the present invention to provide such a machine which utilizes the modular photoconductive assembly belt described in U.S. Pat. No. 4,657,369.
It is yet another object of the present invention to provide such an electrographic printing apparatus which has a simple paper path which can be accessed from the outside to remove paper jams.
As used herein, the term "electrographic printing apparatus" and the like are intended to include copiers, printers and telefax machines which employ a photoconductive member to print information on a sheet of recording medium.